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METAR |
METAR (METeorological Aviation Report) is a format for reporting weather information. A METAR weather report is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting.
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METAR reports typically come from airports or permanent weather observation stations. Reports are typically generated once an hour; if conditions change significantly, however, they can be updated in special reports called SPECIs. Some reports are encoded by automated airport weather stations located at airports, military bases, and other sites. Some locations still use augmented observations, which are recorded by digital sensors, encoded via software, and then reviewed by certified weather observers or forecasters prior to being transmitted. Observations may also be taken by trained observers or forecasters who manually observe and encode their observations prior to transmission.
The METAR format was introduced 1 January 1968 internationally and has been modified a number of times since. North American countries continued to use a Surface Aviation Observation (SAO) for current weather conditions until 1 June 1996, when this report was replaced with an approved variant of the METAR agreed upon in a 1989 Geneva agreement. The World Meteorological Organization's publication No. 782 "Aerodrome Reports and Forecasts" contains the base METAR code as adopted by the WMO member countries.1
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This section may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (May 2008) |
The word METAR originated from the French phrase "message d’observation météorologique régulière pour l’aviation". It is thought to be a contraction of the French words MÉTéorologique ("Weather") Aviation Régulière ("Routine"). The Federal Aviation Administration (FAA) defines a METAR as an aviation routine weather report in the Aeronautical Information Manual (AIM) and would therefore consider it erroneous to attempt to redefine METAR with incorrect terminology (such as METeorological Aerodrome Report).2 The FAA and National Oceanic and Atmospheric Administration (NOAA) specifically define a METAR as an aviation routine weather report, which is an approximate translation of the historical French description.
A typical METAR report contains data for the temperature, dew point, wind speed and direction, precipitation, cloud cover and heights, visibility, and barometric pressure. A METAR report may also contain information on precipitation amounts, lightning, and other information that would be of interest to pilots or meteorologists such as Colour States and RVR.
In addition, a short period forecast called a TREND may be added at the end of the METAR covering likely changes in weather conditions in the two hours following the observation. These are in the same format as a Terminal Aerodrome Forecast (TAF).
The complement to METAR reports, reporting forecast weather rather than current weather, are TAFs. METARs and TAFs are used in VOLMET broadcasts.
METAR code is regulated by Federal Meteorological Handbook No. 1 (FMH-1) and the World Meteorological Organization (WMO) aviation routine weather reports (FM-15 METAR) and aviation selected special weather reports (FM-16 SPECI) codes.
Although the general format of METAR reports is a global standard, the specific fields used within that format vary somewhat between general international usage and usage within North America (specifically the United States and Canada). The two examples which follow illustrate the primary differences between the two METAR variations.3 4
The following is an example METAR from Burgas Airport in Burgas, Bulgaria, and was taken on 4 February 2005 at 16:00 Coordinated Universal Time (UTC).
METAR LBBG 041600Z 12003MPS 310V290 1400 R04/P1500N R22/P1500U +SN BKN022 OVC050 M04/M07 Q1020 NOSIG 9949//91=
North American metars deviate slightly from the WMO (who write the code on behalf of the International Civil Aviation Organization (ICAO)) FM 15-XII code. Details listed in the FAA's Aeronautical Information Manual (AIM). This METAR example is from Trenton-Mercer Airport near Trenton, New Jersey, and was taken on 5 December 2003 at 18:53 UTC.
METAR KTTN 051853Z 04011KT 1/2SM VCTS SN FZFG BKN003 OVC010 M02/M02 A3006 RMK AO2 TSB40 SLP176 P0002 T10171017=
Note that what follows is not part of the international format. This example is particular to the United States, a format not shared with Canada.
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